The present invention relates to a method of making a slitted or particulate absorbent material for absorbent articles such as sanitary napkins, panty liners, absorbent interlabial devices, diapers, incontinence devices, tampons, bandages, wipes, and the like. More particularly, the present invention relates to a method as described above which can be cared out in situ on another component of the absorbent article in a manufacturing process, and can be accomplished without cutting the other component unless it is desired to do so. The present invention also relates to absorbent structures formed by this method.
Absorbent articles such as sanitary napkins, pantiliners, disposable diapers, incontinence products, and bandages are designed to absorb and retain liquid and other discharges from the human body and to prevent body and clothing soiling. Absorbent articles typically comprise a liquid pervious topsheet, a liquid impervious backsheet, and an absorbent core positioned between the topsheet and backsheet. The absorbent core of absorbent articles currently in use can comprise a variety of different types of absorbent materials, including comminuted wood pulp, commonly known as airfelt, creped cellulose wadding; meltblown polymers including coform; chemically stiffened, modified or cross-linked cellulosic fibers; synthetic fibers such as crimped polyester fibers; peat moss; tissue including tissue wraps and tissue laminates; absorbent foams; absorbent sponges; superabsorbent polymers; absorbent gelling materials; or any equivalent material or combinations of materials, or mixtures of these.
In some cases, it has been proposed to slit absorbent material for various purposes. Various methods of slitting materials for different purposes and slit articles are described in the patent literature. European Patent Application 0 234 194 published on Sep. 2, 1987, discloses a method and apparatus for providing sanitary goods with attachment means for attaching to under-clothing which involves slitting a soft and elastic plastic foam sheet. European Patent Specification 0 293 208 B1 discloses forming fluid absorptive material for a catamenial napkin or disposable diaper from a laminate of compressed cellulose-based sponge sheets that have slits provided therein. U.S. Pat. No. 5,397,316 issued to LaVon, et al. discloses absorbent members made of absorbent foam materials that remain relatively thin until wetted which are provided with slitted regions. U.S. Pat. No. 5,611,790 issued to Osborn, et al. discloses extensible absorbent articles which can have an absorbent core that is provided with slits therein.
Known methods of slitting, however, are typically impression related. In such methods, the slitting is done by placing the material to be slit between a sharp cutting blade and a hard backing surface, and cutting the material against the backing surface by applying pressure against the backing surface.
Impression related slitting methods suffer from several drawbacks. The cutting blade will have a high tendency to wear out, particularly if there is metal-to-metal contact between the cutting blade and the backing surface. In addition, with impression related slitting, it is difficult to create narrow strips of slit material (for example, less than xc2xd inch (1.3 cm) wide strips of material) due to the difficulty in arranging the cutting blades sufficiently close together to create such narrow strips. Another disadvantage is that there are limitations to the location of the slitting operation in the process of making an absorbent article. It is generally difficult to slit a web of material after it is combined with another web of material without slitting both materials. While it is possible to slit only one web of such a combined web, great care has to be taken in setting the distance between the cutting blade and the backing surface so that only one of the webs is slit.
It has also been proposed to use particulate absorbent material in absorbent articles. However, the only known methods for providing a particulate absorbent material for an absorbent core involve a step of chopping the absorbent material to form particulate absorbent material, then transferring the chopped absorbent material to a delivery system for delivering the absorbent material to the absorbent core, providing a suitable receptacle to contain the particulate absorbent material, and delivering the chopped absorbent material to the receptacle.
Often, the delivery system for providing particulate absorbent material will involve mixing the particulate material in a stream of air and using the air to blow the particulate material into the receptacle for the absorbent material. This will generally require that the receptacle be closed on all sides to prevent the particles from being blown outside the receptacle. It will also require that the quantity of the absorbent material particles delivered to the absorbent article be controlled (or xe2x80x9cmeteredxe2x80x9d).
These known methods for providing particulate absorbent material suffer from numerous drawbacks. They involve a substantial number of steps. They require the use of a delivery system, which typically must be a closed system so that the particles can be mixed in a stream of air. They require a supply of compressed air, and a closed receptacle to receive the particulate material.
Thus, a need exists for an improved method of making and providing a slitted or particulate absorbent material for absorbent articles.
The present invention is directed to a method of making a slitted or particulate absorbent material for an absorbent article such as sanitary napkins, diapers, incontinence devices, tampons, bandages, wipes, and the like. More particularly, the present invention relates to a method as described above which can be carried out in situ on another component of the absorbent article in a manufacturing process, and can be accomplished without cutting the other component unless it is desired to do so.
The present invention can be used even more broadly to break (fracture, fragment, or otherwise alter the integrity of) an absorbent material. This is particularly the case if it is not necessary to slit the material along pre-defined lines or to form the absorbent material into particulate material. The method of the present invention can break an absorbent material in a composite web without breaking the outer carrier web(s) by the application of a force on the composite web. The force applied to the composite web can be a tensile force, a compressive force, or both. If both of these types of forces are used, they can be applied either simultaneously, or sequentially (in either order). A large number of different processes and types of apparatus can be used to apply the force to the composite web. Suitable types of processes include, but are not limited to passing the composite web through a nip between grooved or patterned rolls, embossing (against a rigid or deformable surface), compression between mating plates, vacuum, or other methods for exerting a force on a material.
In one preferred embodiment, the method of making a slitted or particulate absorbent material comprises the steps of:
(a) providing a carrier web having a first breaking point;
(b) providing a second material on the carrier web to form a composite web having two surfaces, which second material has a second breaking point that is lower than the breaking point of the carrier web, and comprises an absorbent material;
(c) providing an apparatus for applying localized forces on portions of the composite web; and
(d) applying a force to at least a portion of at least one of the surfaces of the composite web using the apparatus, which force is greater than the second breaking point, but less than the first breaking point so that the second material breaks in at least one place without breaking the carrier web.
In a particularly preferred embodiment, the absorbent material is an absorbent foam that is wrapped inside a nonwoven carrier web. The force applied by the apparatus breaks the inner absorbent material (due to its greater destructibility), but only deforms the outer nonwoven web to provide a self-contained web of particulate material inside a nonwoven wrapping. The present invention provides an improved method of making and providing a self-contained slitted or particulate absorbent material for absorbent articles. The method of the present invention involves very few steps and significantly less additional equipment, and does not require a delivery system that uses compressed air to transport particulate material to a closed receptacle. The method of the present invention also eliminates the need to re-meter the quantity of the particulate material delivered to the absorbent article.
The present invention also relates to absorbent structures formed by this method. In one embodiment, the absorbent structure comprises a composite web of discrete elements of absorbent material. The composite web comprises at least one carrier web and a plurality of discrete elements of absorbent material arranged in an orderly array on the carrier web. In such an embodiment, the discrete elements of absorbent material can be positioned adjacent to each other without any intervening material between the discrete elements of absorbent material. In other embodiments, portions of the carrier web can be extended down between the discrete elements of absorbent material. In these or other embodiments, the composite absorbent structure can be extensible, stretchable, and/or elastically extensible. The absorbent structures of the present invention provide numerous advantages. These include, but are not limited to: providing a composite structure with improved flexibility and/or conformability to a wearer""s body; improving the softness of the structure; improving the distribution of particulate absorbent material within the structure; and, improving the acquisition and handling of bodily fluids.